556
FXUS63 KILX 132314
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
614 PM CDT Mon Oct 13 2025

.KEY MESSAGES...

- The next chance for widespread rainfall is slated for next
  weekend. The latest NBM guidance has become a bit more
  optimistic...with probabilities for greater than half an inch
  increasing to 50-60% across most of central Illinois.

- There is a 15% chance for severe thunderstorms Saturday
  afternoon and evening...mainly along and south of a Springfield
  to Robinson line.

&&

.SHORT TERM...(Tonight through Tuesday)
Issued at 229 PM CDT Mon Oct 13 2025

18z/1pm surface analysis shows a weak cold front crossing the
Mississippi River. The band of very light showers from earlier
today has pushed eastward to the Indiana border and diminished
significantly...but a few sprinkles will remain possible
along/east of I-57 for the next couple of hours. Further west
along the front, no precipitation is observed...although a band of
Cu has formed. The front will continue to lose forward momentum as
it shifts slowly eastward and essentially stalls across the area
tonight. Given minimal forcing along the boundary and very weak
upper dynamics, am expecting little more than an increase in cloud
cover later this evening through the overnight hours across the
W/NW half of the KILX CWA. NAM/RAP forecast soundings indicate a
dry boundary layer with a pinch of moisture developing from
5000-8000ft aloft. The clouds will be most prevalent near the
front along/north of a Rushville to Bloomington line...while
locations further S/SE should remain partly cloudy. While soundings
and CAM guidance do not really support it, am concerned that fog
may form across areas that saw the light showers today...particularly
where it does not become completely overcast. As a result, have
added patchy fog along/south of a Rushville to Bloomington
line...and north of a Taylorville to Champaign line. After any
early morning fog dissipates, am expecting partly to mostly cloudy
conditions across the N/NW CWA with mostly sunny skies further
SE on Tuesday. Lows tonight will range from the lower 50s near
the Indiana border to around 60 in the Illinois River Valley.
Highs on Tuesday will range from the middle 70s far northwest
around Galesburg to the lower 80s along/south of I-70.

Barnes

.LONG TERM...(Wednesday through Next Monday)
Issued at 229 PM CDT Mon Oct 13 2025

A mostly uneventful work week lies ahead as central Illinois
remains under the influence of prevailing upper-level ridging.
After a slight cool-down into the lower to middle 70s on
Wednesday, readings will climb back into the upper 70s and lower
80s by Friday.

After that, the weather becomes more active over the weekend as a
cut-off low progged to form over northern California on Monday
gradually opens and lifts northeastward by the end of the week. As
this process unfolds, deep-layer southwesterly flow will develop
across the Plains/Midwest. This will help pull better moisture
into the region and result in a more significant chance for
rainfall from Friday night through Sunday. The GFS remains about 6
hours faster with its FROPA midday Saturday, while the ECMWF/GEM
are both slower. Given the highly amplified pattern in place and
the strength of the upper ridge, think the slower solutions are
prudent. With that said, showers and perhaps a few thunderstorms
will push into the Illinois River Valley late Friday night...with
re-development of showers/storms mainly east of I-55 Saturday
afternoon/evening. With deeper moisture in place and strong upper
dynamics ahead of the approaching upper wave, strong to
potentially severe thunderstorms may develop during peak heating
if the slower ECMWF/GEM verify. The 00z LREF shows about a 20%
chance of SBCAPEs exceeding 500J/kg and 0-500mb bulk shear greater
than 30kt by 00z Sun along/south of a Springfield to Robinson
line. As a result, the latest SPC Day 6 Outlook highlights this
area for a 15% chance for severe on Saturday.

The next forecast question will be how much rainfall will occur
with the weekend system. Synoptic models often handle antecedent
dry soil conditions quite poorly, so raw QPF from any model at
this point should be taken with a grain of salt. In addition, if
severe weather becomes widespread further south across the Ozarks
into western Kentucky where parameters are more favorable, this
could potentially intercept some of the Gulf moisture flowing
northward. While NBM probabilities for greater than 0.50 have
increased to 50-60% across most of central Illinois, think this
may be a bit too optimistic given the mitigating factors in play.
Feel that the best bet for significant rainfall from this system
will be along/south of I-70 where probs for more than 1 inch of
rain have nudged up into the 40-50% range.

Barnes

&&

.AVIATION...  (For the 00z TAFs through 00z Tuesday Evening)
Issued at 614 PM CDT Mon Oct 13 2025

A weak cold front will continue to settle southward and stall
across the area tonight. This should bring fairly widespread cloud
cover based at 4000-6000 ft AGL, but little chance for any
rain. Conditions should remain VFR, but areas near where light
rain was received in the past day could see patchy fog if any
significant breaks in cloud cover develop, reducing vsby to MVFR
or worse. Any fog would most likely be near and north of I-72. At
this time, chances of this appear too low for mention in TAFs,
but this will need to be watched for. Winds SE 3-7 kts, becoming
light and variable this evening. NE winds 4-8 kts developing by
09Z-12Z.

37

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$